The alkyllithium-mediated decomposition of arenesulfonylhydrazones (i.e., the Shapiro reaction) is certainly one of the most powerful methods for regioselective preparation of alkenes via alkyllithium reagents. In this reaction, reactive species may be generated in situ from arenesulfonylhydrazones under conditions of excess base at low temperature. The intermediates can be trapped in reasonable yield with common electrophiles (e.g. protons). We have successfully used this approach to facilitate deuterium or tritium labelling in the following manner ketones containing an a-methylene group (e.g. steroids) are converted to their hydrazone derivative, and then into dianions using alkyllithium bases at -78 C, and the vinyl anions are then quenched with isotopic water at 0oC. We have found that tosylhydrazone derivatives are not appropriate for deuterium and tritium labelling applications since the tosyl methyl protons are readily exchangeable under basic conditions, and lead to isotopic dilution in the labelled product. By use of triisopropylbenzene-sulfonylhydrazones (trisylhydrazones), the reaction conditions are substantially changed the need for excess base is eliminated, and the formation of the dianion intermediate is accelerated to the point that THF may be used as a solvent. During the course of this project we also found that the use of t-BuLi in pentane as a base for the generation of vinyllithium intermediates is essential in the production of high specific activity olefins. The use of another common base, methyllithium in ether, leads to low specific activity products, presumably caused by the abstraction of hydrogen from ether during the reaction. After preliminary successful experiments with deuteriated water, this labelling approach was extended to tritium labelling. The trisylhydrazone derivatives of a variety of ketones such as 4-phenylcyclohexanone, cyclododecanone, cholest-4-en-3-one (a,b-unsaturated ketone) and 3-methoxy estrone served as the substrates. In each experiment, the substrate was dissolved in dry THF, the vinyllithium intermediate was generated in situ in the presence of t-butyllithium at -78oC and was then quenched with highly tritiated water at 0oC. The labelled olefin product was isolated and analyzed by radio-HPLC, radio-GC, LSC and proton and tritium NMR spectroscopy. By this combination of analytical techniques, the specific radioactivity and chemical yields of all the compounds were determined. Specific activities in the range of 14-23 Ci/mmole were obtained, varying with the substrate. In this project we have demonstrated a useful and general tritiation technique for the synthesis of tritiated alkenes. The demonstration phase of this project is complete, and a manuscript entitled "Tritium Labelled Alkenes via the Shapiro Reaction" was published in Tetrahedron Letters.